A new species of the genus Proasellus (Crustacea: Isopoda: Asellidae) from the Abin River basin, with the preliminary data on the diversity of the genus in the southwestern foothills of the Russian Caucasus

Invertebrate Zoology, 2024, 21(1): 81–93 © INVERTEBRATE ZOOLOGY, 2024 A new species of the genus Proasellus (Crustacea: Isopoda: Asellidae) from the Abin River basin, with the preliminary data on the diversity of the genus in the southwestern foothills of the Russian Caucasus Ivan N. Marin1*, Sergey Yu. Sinelnikov2 1 A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky prospekt 33, Moscow 119071 Russia. E-mail: [email protected] 2 Papanin Institute for the Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl Region 152742 Russia. E-mail: [email protected] * corresponding author Ivan Marin: ORCID: 0000-0003-0552-8456 Sergey Sinelnikov: ORCID: 0000-0003-4188-4589 ABSTRACT. A new stygobiotic species of the genus Proasellus Dudich, 1925 (Crustacea: Isopoda: Asellidae), Proasellus abini sp.n., is described from the hyporheic habitats and groundwater of the Abin River basin, located in the southwestern foothills of the Caucasian Ridge. The new species is morphologically and genetically close to Proasellus linearis Birštein, 1967, known from the Evstafiev Sсhel (=Ashamba River) near Gelendzhik. Data on phylogeny, ecology and feeding of the species and other SW Caucasian species of the genus are also presented in the paper. How to cite this article: Marin I.N., Sinelnikov S.Yu. 2024. A new species of the genus Proasellus (Crustacea: Isopoda: Asellidae) from the Abin River basin, with the preliminary data on the diversity of the genus in the southwestern foothills of the Russian Caucasus // Invert. Zool. Vol.21. No.1. P.81–93. doi: 10.15298/invertzool.21.1.04 KEY WORDS: Crustacea, diversity, Proasellus, new species, hyporhea, stygobiotic, southwestern Caucasus, Russia. Новый вид рода Proasellus (Crustacea: Isopoda: Asellidae) из бассейна реки Абин, с предварительными данными по разнообразию рода из юго-западных предгорий российского Кавказа И.Н. Марин1*, С.Ю. Синельников2 1 Институт проблем экологии и эволюции им. А.Н. Северцова РАН, Ленинский проспект, 33, Москва 119071 Россия. E-mail: [email protected] 2 Институт биологии внутренних вод им. И.Д. Папанина РАН, Борок, Ярославская обл. 152742 Россия. E-mail: [email protected] * Автор для переписки РЕЗЮМЕ. Новый стигобионтный вид рода Proasellus Dudich, 1925 (Crustacea: Isopoda: Asellidae), Proasellus abini sp.n., описывается из гипогейных биотопов и подземных вод бассейна реки Абин, расположенной в юго-западных предгорьях Кавказского хребта. Новый вид морфологически и генетически близок к Proasellus linearis Birštein, 1967, известному из Евстафьевской щели (= река Ашамба) близ Геленджика. В статье также представлены данные о филогении, экологии и питании этого вида и других представителей рода с юго-западных предгорий Кавказа. I.N. Marin, S.Yu. Sinelnikov82 Introduction Groundwater ecosystems are among the most understudied habitats of our planet (Saccò et al., 2023). Current knowledge on the diversity of subterranean and hyporheic crustaceans of the Caucasus is still fragmentary, despite the fact that quite a lot of publications with a description of stygobiotic diversity have appeared recently (Marin, 2017, 2019, 2020; Marin, Palatov, 2019a, 2023a, b; Grego et al., 2020; Palatov, Sokolova, 2021; Marin et al., 2021b, 2022, 2023; Rendoša et al., 2021; Anistratenko et al., 2022; Palatov et al., 2023). Most likely the reason is that Caucasus is the second region of the Western Palearctic (after the Balkan Peninsula) in terms of the size of karst area, the variety of landscapes and climatic conditions (Myers et al., 2000; Krever et al., 2001), as well as groundwateradapted biodiversity is mainly composed of short-range species with restricted distributions (Trontelj et al., 2009; Eme et al., 2018). Most of the hyporheic crustaceans of the Caucasus are narrowly endemic (Marin et al., 2021; Palatov, Marin, 2021). It is also important that the study of groundwater organisms is hindered by the inaccessibility and complexity of their collection. The genus Proasellus Dudich, 1925 (Crustacea: Isopoda: Asellidae) is one of the most diverse and most widely distributed genera of groundwater crustaceans in the western Palaearctic, currently including about 125 valid species (Boyko et al., 2023). The understudy in the Caucasus is also true for this group of crustaceans, especially in the western part of the Caucasus Mountains. Currently only 7 species of the genus Proasellus are known from different localities in the Caucasus, mostly described by J.A. Birštein (1936, 1967) (after Palatov, Sokolova, 2021; Palatov et al., 2023). At the same time, only one species of this genus has been described, namely Proasellus linearis Birštein, 1967 from the western foothills of the Caucasus, exactly from the Evstafiev Sсhel near Gelendzhik (Birštein, 1967). This location most likely refers to the sources of the small mountainous river Ashamba (Yashamba), originating on the southern slope of the Markhoth Ridge and flowing into the Black Sea in the Blue Bay area (Gelendzhik). The endemism of this area has already been shown on another group of hyporheic crustaceans, representatives of the genus Niphargus Schiödte, 1849 (Crustacea: Amphipoda: Niphargidae) (Marin et al., 2021a) and representatives of the genus Lyurella Derzhavin, 1939 (Crustacea: Amphipoda: Crangonyctidae) (Marin, Palatov, 2021b). Recent sampling of representatives of the genus Proasellus have shown that they are much more diverse than previously thought, inhabiting the hyporhea of all large rivers in the area. In this article we present data on the molecular diversity, distribution, ecology of representatives of the genus in the western foothills of the southwestern Caucasus, as well as describe a new species from the Abin River basin and nearby small mountainous rivers. Material and Methods SPECIMEN SAMPLING and MORPHOLOGICAL STUDY. Groundwater isopods were collected by hand net in springs and wells in the foothill area of the southwestern Caucasus (see Fig. 1). All specimens were fixed in 70–90% solution of ethanol. The type material is deposited in the collection of Zoological Museum of Moscow State University, Moscow (ZMMU) and author’s collection in A.N. Severtsov Institute of Ecology and Evolution of Russian Academy of Sciences, Moscow, Russia (LEMMI). The body length (bl., in mm), the dorsal length from the anterodorsal margin of the head to the margin of the pleotelson, without the length of uropods and antennas, was used as a standard measurement. Line drawings were made using camera lucida attached to Olympus SZX10 light stereomicroscope. MOLECULAR STUDY. A fragment of the mitochondrial gene coding for cytochrome c oxidase subunit I (COI mtDNA) gene marker was amplified with the help of the universal primers LCO1490 Как цитировать эту статью: Marin I.N., Sinelnikov S.Yu. 2024. A new species of the genus Proasellus (Crustacea: Isopoda: Asellidae) from the Abin River basin, with the preliminary data on the diversity of the genus in the southwestern foothills of the Russian Caucasus // Invert. Zool. Vol.21. No.1. P.81–93. doi: 10.15298/invertzool.21.1.04 КЛЮЧЕВЫЕ СЛОВА: ракообразные, разнообразие, Proasellus, новые виды, гипогея, стигобионтный, юго-западный Кавказ, Россия. A new Proasellus from the Abin River basin 83 Fig. 1. Map of collection sites and phylogenetic relationships of Proasellus abini sp.n. Bootstrap support of all nodes is reported. Рис. 1. Карта мест сбора и филогенетические взаимоотношения Proasellus abini sp.n. Поддержка узлов (клад) представлена. (5’-ggtcaacaaatcataaagatattgg-3’) and HC02198 (5’-taaacttcagggtgaccaaaaaatca-3’) (Folmer et al., 1994). The obtained sequences of the new species are deposited in the GenBank (NCBI) database for the further genetic studies. The aligned sequences of COI mtDNA gene markers, 658 base pairs in length, were analyzed for pairwise sequence divergence (uncorrected p–distances) with the sequences of the related species, deposited in GenBank (NCBI) database using MEGA 7.0 (Kumar et al., 2016). Only Caucasian species of the genus Proasellus were used for the phylogenetic analysis. The best evolutionary substitution model was determined using MEGA 7.0. and jModeltest2.1.141 (Diego Darriba, Universidade da Coruña as part of the Computer Architecture Group (GAC), Coruña, Spain) on XSEDE via the CIPRES (Cyber Infrastructure for Phylogenetic Research) Science Gateway V. 3.3 (http://www.phylo.org/, accessed on 10 September 2023). Phylogenetic analysis was performed using PhyML 3.0 (Guindon et al., 2010) using GTR+G+I model for Maximum-Likelihood analysis (ML). Uncorrected pairwise genetic divergence (pdistances) was calculated using MEGA 7.0 with the Kimura 2‐Parameter (K2P) model of evolution (Kimura, 1980). STABLE ISOTOPE ANALYSIS. Material for the analysis of stable isotope (δ13C/δ15N) was collected in springs of Novorossiyskaya Schel, 44°44′27.39″N 37°54′03.71″E. The muscles tissues of collected animals were oven-dried at 50 °С for 4–5 days, and then were wrapped in tin foil (1200–1500 µg and 400–600 µg, respectively). The isotopic composition was determined using a Thermo-Finnigan Delta V I.N. Marin, S.Yu. Sinelnikov84 Table 1. Pairwise genetic (COI mtDNA) distances (p-distances) (substitutions per 100 nucleotides) of Proasellus adegoyi sp.n. and congeners from the Russian Caucasus. Таблица 1. Попарные генетические (COI мтДНК) расстояния (p-дистанции) (замены на 100 нуклеотидов) Proasellus adegoyi sp.n. и родственных видов с Российского Кавказа. Proasellus abini sp.n. (Abin River Basin) P. linearis Pshada Basin Mezyb Basin Vulan Basin P. liovuschkini Vorontsovka сaves P. irystonicus P. precaspicus P. linearis 0.086 Proasellus sp. Pshada Basin 0.112 0.089 Proasellus sp. Mezyb Basin 0.120 0.93 0.087 Proasellus sp. Vulan Basin 0.124 0.103 0.110 0.091 P. cf. liovuschkini 0.153 0.132 0.127 0.103 0.141 Proasellus sp. Vorontsovka сaves 0.170 0.180 0.199 0.171 0.187 0.196 P. irystonicus 0.145 0.144 0.139 0.099 0.154 0.147 0.188 P. precaspius 0.151 0.149 0.133 0.141 0.137 0.169 0.181 0.154 Proasellus sp. KarachaevoCherkessiya 0.128 0.130 0.121 0.111 0.125 0.122 0.175 0.131 0.101 A new Proasellus from the Abin River basin 85 Plus continuous-flow mass spectrometer (Thermo Electron GmbH, Bremen, Germany) coupled with an elemental analyzer (Thermo Flash 1112, Thermo Electron) at the Joint Usage Center at the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences. The isotopic composition of N and C was expressed in the δ-notation relative to the international standard (atmospheric nitrogen or VPDB): δX(‰) = [(Rsample/Rstandard) − 1] × 1000, where R is the ratio of the heavier isotope to the lighter isotope. Samples were analyzed with reference gases calibrated against IAEA (Vienna, Austria), reference materials USGS 40 and USGS 41 (glutamic acid). The drift was corrected using internal laboratory standards (acetanilide, casein). The standard deviation of δ15N/δ13C values in are laboratory standards (n=8) was <0.15‰. Standard abbreviations: A — antenna; Ep — epimeral plate; Gn — gnathopods; M — maxilla; Mx — maxilliped; P — pereo pod; PL — pleopod; Pp — pereopods; T — telson; U — uropod; Ur — urosomite. Results PHYLOGENETIC DATA. The interspecific genetic divergence of the new species is the lowest comparing with P. linearis from Ashamba, representing about 0.086 substitutions per 100 nucleotides (8.6%), while the divergence from other Caucasian congeneric species reaches more than 10% (see Table 1), which indicates prolonged isolation and the absence of a gene flow. Phylogenetically the new species is also close to P. linearis, probably being its sister species (see Fig. 1). At the same time, all SW Caucasian species of the genus Proasellus represent the monophyletic clade, with the species inhabiting hyporhean and underground habitats in the basins of different local mountainous rivers, such as Ashamba, Abin, Pshada, Mezyb, Vulan, which were separated during last 2 Mya in the result of mountain grow. TROPHIC POSITION BASED ON ISOTOPIC ANALYSIS. The studied new species, Proasellus abini sp.n., is situated in the low tropic position (–22.67±0.12 for δ13C and 4.40±0.32 for δ15N) close to primary herbivorous animals in the general scheme of isotopic values of δ13C and δ15N for macrozoobenthos (see Marin et al., 2021a). The similar trophic position is characteristic for herbivorous crustaceans co-occurring in the springs of the Novorossiyskaya Schel, such as undescribed species of the genus Niphargus from the “tauricus” species complex (Amphipoda: Niphargidae), Synurella adegoyi Marin et Palatov, 2022 (Amphipoda: Crangonyctidae) (see Marin & Palatov, 2022) and Gammarus cf. komareki Schäferna, 1923 (Amphipoda: Gammaridae), which are probably feed on primary organic matter, like the remains and roots of various forest plants that fall into the hyporhea and groundwater (pers. observ.; unpublished). Taxonomic account Isopoda Latreille, 1817 Suborder Asellota Latreille, 1802 Family Asellidae Rafinesque-Schmaltz, 1815 Genus Proasellus Dudich, 1925 Proasellus abini sp.n. Figs 2D–F, 3–5. MATERIAL EXAMINED. Holotype: ♀ (bl. 6.2 mm), ZMMU Mc-1458, Russian Federation, southwestern Caucasus, Krasnodar Krai, Gelendzyk area, the upper stream of the Adegoy River, Novorossiyskaya Schel, 44°44′27.39″N 37°54′03.71″E, in the river hyporheic habitats, hand net sampling, coll. I. Marin, S. Sinelnikov & S. Marina, 8 Nov. 2021. Paratypes: ♀ (bl. 5.5 mm), ♂ (bl. 6.0 mm), ZMMU Mc-1459, Russian Federation, south-western Caucasus, Krasnodar Krai, Krymsky district, the upper stream of the Shids River, 44°48′09.03″N 37°59′26.54″E, inside a small well, coll. I. Marin, S. Marina, 24 July 2021. Other material: Russian Federation, south-western Caucasus, Krasnodar Krai: 2♀♀, 6♂♂, LEMMI, Abin area, the upper stream of the Abin River, 44°43′32.3″N 38°10′04.5″E, coll. I. Marin, S. Marina, 12 Aug. 2021; 5♀♀, 7♂♂, LEMMI, the upper stream of the Adegoy River, Afonka, 44°42′53.2″N 37°58′27.1″E, in the river hyporheic habitats, hand net sampling, coll. I. Marin, S. Marina, 18 July 2021; 2♀♀, 4♂♂, LEMMI, Abin area, Adegoy River, near Shapsugskaya village, 44°43′31.8″N 38°02′13.8″E, in the river hyporheic habitats, hand net sampling, coll. I. Marin, S. Marina, 19 July 2021; 5♀♀, 6♂♂, LEMMI, Abin area, Abin River, Shapsugskaya village, 44°45′30.2″N 38°04′50.0″E, in the river hyporheic habitats, hand net sampling, coll. I. Marin, S. Marina, 19 July 2021; 3♀♀, 6♂♂, LEMMI, Abin river, 44°43′43.6″N 38°06′35.6″E, in the river hyporheic habitats, hand net sampling, coll. I. Marin, S. Marina, 3 Aug. 2021. ETYMOLOGY. The new species is named after the Abin River (SW Caucasus), in the basin of which the new species was discovered. DIAGNOSIS. Medium-sized, depigmented species. Head bisinuate, medially concave, about 1.4 I.N. Marin, S.Yu. Sinelnikov86 Fig. 2. General view and natural habitat of Proasellus abini sp.n.: A — a forest well, Shids, general view; B, C — individuals of the new species on the bottom and walls of the well; D, F — general dorsal view of alive individual of the new Proasellus abini sp.n. and its lateral view (E). Рис. 2. Общий вид и природные местообитания Proasellus abini sp.n.: A — лесной колодец, Шидс, общий вид; B, C — особи нового вида на дне и стенках колодца; D, F — общий дорсальный вид живой особи Proasellus abini sp.n. и ее вид сбоку (E). A new Proasellus from the Abin River basin 87 Fig. 3. Proasellus abini sp.n., ♂ from the hyporhean habitats of the upper stream of Adegoy river (right tributary of Abin river), Novorossiyskaya Schel: A — both antenna I and II; B — antenna I; C — distal flagellum of antenna I; D — labium; E — labrum; F — right mandible; G — pars incisiva (incisor) of right mandible; H — maxilla; I — maxillula; J — maxilliped. Рис. 3. Proasellus abini sp.n. ♂ из гипогеи верхнего течения реки Адегой (правого притока реки Абин), Новороссийская щель: A — антенны I и II; B — антенна I; C — дистальный жгутик антенны I; D — лабиум (нижняя губа); E — (лабрум) верхняя губа; F — правая мандибула; G — резцовый отросток правой мандибуды; H — максилла; I — максиллула; J — максиллипед. I.N. Marin, S.Yu. Sinelnikov88 Fig. 4. Proasellus abini sp.n., ♂ from the hyporhean habitats of the upper stream of Adegoy river, Novorossiyskaya Schel: A — pereopod I; B — dactylus of PI; C — pereopod II; D — dactylus of PII; E — pereopod III; F — dactylus of PIII; G — pereopod IV; H — dactylus of PIV; I — pereopod V; J — dactylus of PV; K — pereopod VI; L — dactylus of PVI; M — pereopod VII; N — dactylus of PVII. Рис. 4. Proasellus abini sp.n., ♂ из гипогеи верхнего течения реки Адегой, Новороссийская щель: A — переопода I; B — дактилус PI; C — переопода II; D — дактилус PII; E — переопода III; F — дактилус PIII; G — переопода IV; H — дактилус PIV; I — переопода V; J — дактилус PV; K — переопода VI; L — дактилус PVI; M — переопода VII; N — дактилус PVII. A new Proasellus from the Abin River basin 89 Fig. 5. Proasellus abini sp.n., ♂ (A–C, E, F, G, H) and ♀ (D, I) from the hyporhean habitats of the upper stream of Adegoy river, Novorossiyskaya Schel: A — pleopod I; B — retinacula on medial margin of protopodite of PLI; C — pleopod II (♂); D — pleopod II (♀); E — pleopod III (♂); F — pleopod IV and V (♂); G — pleotelson; H, I — uropod. Рис. 5. Proasellus abini sp.n., ♂ (A–C, E, F, G, H) и ♀ (D, I) из гипогеи верхнего течения реки Адегой, Новороссийская щель: А — плеопода I; B — ретинакула на медиальном краю протоподита PLI; C — плеопода II (♂); D — плеопода II (♀); E — плеопода III (♂); F — плеопода IV и V (♂); G — плеотельсон; H, I — уропода.